This invention relates to a method for giving a locomotion-command system for mobile robots such as unmanned travelling vehicles.
There have been proposed various methods for making unmanned mobile robots travel; one method comprises the steps of emitting inductive radio waves of a predetermined frequency from an induction wire and making a mobile robot receive the radio waves to travel along the route formed by the induction wire. Another method uses an optical reflective tape and a photoelectric detector instead of the induction wire. These methods require guiding means, as the mobile robot of this type are controlled and guided by detecting and compensating deviation from the route of the induction wire or the photoelectric reflective tape which is laid on a floor. When the layout of tools and machineries and/or facilities in a plant or a warehouse are revised, the conveyor route formed among such facilities should be changed accordingly, which inconveniently needs replacing the guiding means again. Further in the case of the method using an induction wire, it takes much time and trouble in laying and burying the wire. The method using a photoelectric reflective tape has another disadvantage that it is prone to dust and easily stained or damaged.
Japanese patent laid-open No. 62424/1982 discloses a travel-command method which obviates aforementioned detriments. In the method, the route along which a mobile object is to travel is expressed by a sequence of points with X-Y coordinates, which are generated in a form of digital data, with which a region is determined. The region and an assumed position ahead in the advancing direction determine a region to which the object is to advance. A steering signal is generated based upon a point on a line connecting at least two points included within the specified region and the assumed position of the moving object ahead thereof. However, as the advancing route is expressed with a sequence of points with coordinates in this method, it is not possible to smoothly specify or to control the route when the travel-lane should change from a line 1 to another parallel line 2 as shown in FIG. 1A, or when the object should make a U-turn and return on a same route 3 as shown in FIG. 1B.